1. Field of the Invention
The present invention is directed to photoinitiated cationic epoxy compositions having good impact strength and toughness.
2. Brief Description of Related Technology
Photoinitiated, cationically curable adhesive compositions based on epoxy resins have many benefits and advantages desirable to end user consumers. For example, such compositions provide cured products having physical properties comparable to those provided by thermosetting compositions, are less inhibited by oxygen than photoinitiated free radical curable compositions (resulting in faster and more thorough cure), and exhibit less shrinkage during cure than otherwise comparable photoinitiated free radical curable compositions (such as those based on acrylic chemistry).
Photoinitiated cationic adhesive compositions have, therefore, been used in various well-known applications such as liquid crystal displays and as laminates in digital video discs.
There has been an ongoing desire to find photoinitiated adhesive compositions having good impact strength and toughness, because photocure mechanisms are ordinarily more rapid than heat cure mechanisms and can avoid heat degradation of the overall device, part and/or substrate.